Securities (Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Securities
AFS securities, debt securities due in one year or less, amortized cost	$ 189
AFS securities, debt securities due in one year or less, fair value	189
AFS securities, debt securities due after one year through five years, amortized cost	565
AFS securities, debt securities due after one year through five years, fair value	573
AFS securities, debt securities due after five years through ten years, amortized cost	499
AFS securities, debt securities due after five years through ten years, fair value	519
AFS securities, debt securities due after ten years, amortized cost	20,915
AFS securities, debt securities due after ten years, fair value	20,823
Total AFS debt securities, amortized cost	22,168
Total AFS debt securities, fair value	22,104
HTM securities, debt securities due after five years through ten years, amortized cost	5,926
HTM securities, debt securities due after five years through ten years, fair value	5,524
HTM securities, debt securities due after ten years, amortized cost	12,175
HTM securities, debt securities due after ten years, fair value	12,006
Total HTM debt securities, amortized cost	18,101
Total HTM debt securities, fair value	$ 17,530